Immune System

Non-Specific Immunity

• Lysozyme – digests cell walls• Skin (physical barrier)• Stomache Acidity• Phagocytes (roam body for bacteria/dead cells)

– Macrophages (long lived, generate toxic forms of oxygen)– Neutrophils (60-70% of white blood cells, self destruct)

• Complement Protein (coats cells to attract phagocytes)• Inflammation

– Histamine (initiates inflammation)• Causes increased blood flow and increased permeability to the

injured tissue.

Specific

• Lymphocytes (produced from stem cells)– T cells

• Mature in thymus• 2 types, Helper T cells and Cytotoxic T cells• Cytotoxic T’s involved in cell-mediated immunity

– B cells• Mature in bone marrow• 2 Types, plasma cells and memory B cells.• Plasma Cells

– Factories that produce antibodies (Humoral immunity)

• Memory B cells (secondary immune response)– Recognize old invaders and produce antibodies immediately. (produces in a

much larger concentration than in primary response.

• Primary Immune response– Helper T’s help activate B cells; T cells recognize foreign antigens on surface of

phagocytic cells and bind to them. After binding they multiply and pump chemical signals to bring B cells.

Cell-mediated immunity

• Cells infected with viruses produce viral antigens. Some appear on the cell surface.– Cytotoxic cells recognize these and destroy them.

• Class I histocompatability antigens (MHC)– All cells within a person’s body have this (except red blood cells),

anything the immune system finds that doesn’t have a matching MHC registers as foreign.

– Class II histocompatability antigens are on immune cell.• Play a role in immune cell communication.

• Every B cell has a specific antigen recognition site on its surface. B cells patrol the body for a particular invader. When a B cell meet and attaches its appropriate antigen, it activates and the B cell undergoes mitosis and differentiation into plasma cells and memory cells.

Antibodies (Humoral Immunity)

• Antibodies– 2 ends; Fragment antigen binding region (Allows antibodies to recognize specific antigens),

5 types of antibodies for different cells types (IgA, IgD, IgE, IgM, IgG) Ig=immunoglobulin; Other end binds to effector cells.

– Epitope (Small accessible portion of antigen)

• Forms of attack– Neutralization

• Binds and blocks

– Opsonization• Enhance macrophage attachment to microbes

– Agglutination (Clumping)• Combines both processes

Complement Fixation (Disposal)

• Proteins cause viruses and pathogenic cells to lyse so that they may be cleaned.

• Membrane attack complex (MAC)

• 2 Paths– Classic Pathway

• The lysing is caused by antibodies

– Alternative pathway• The lysing is caused by already present

substances.

Active Immunity

• Depends on the response of a person’s own immune system. (Ex. Vaccine)

• Passive Immunity– Transfer of one person’s antibodies into

another person. (Temporary)

Blood Types

• ABO blood groups– A blood has a antigens on surface, B has B,

and O has none.

• Rh Factor– Produces IgG antibodies which produce

memory cells. Causes a problem in pregnancies when a mother is negative and children are negative, especially after the first born.

Allergies

• Hypersensitive responses to environmental antigens. Induces in mast cells to degranulate (release histamine and inflammatory agents.)

• Anaphylactic shock– Widespread mast cell degranulation, triggers

dilation of peripheral blood vessels, and causes a significant drop in blood pressure.

Immunodeficiency diseases

• SCID (Severe combined immunodeficiency)– Cell mediated and humoral immune defenses fail

• AIDS– Collapses immune system by targeting and destroying

helper T cells and its coreceptor fusin, which is also found on macophages.

– Chemokins• Suppress HIV-1 infection by blocking the receptors that

HIV bind to.

• Moods release hormones that may impair or enhance immunity